Copperbands are very delicate fish to begin with. They also have extreme issues with eating. They get stressed very easily and combined with their lack of eating usually dictates why they dont make it. I had one that lasted well over a year until I accidentally killed it with an overdose of flatworm exit. :-( Since then I have tried on three different occassions to keep one all three with no success.
I take ultra care of my fish, I feed whatever I need to and take great care in selecting tankmates and yet the three died within weeks of adding them.
The one I did have that thrived i attribute to the care it received at the lfs
before i took him home. he was wt'd for 3 months and trained to eat by hand, he was an awesome, maybe one in a million fish. Some people can get lucky with them but a cast majority do not do well in home aquaria.
Really sorry yours didnt make it, its always very sad when something we love and put effort into doesnt so well like we had hoped.